The present invention relates to conveyor belt sealing systems which are used to seal against the escape of bulk materials, such as sand, gravel or coal, which are being loaded upon a conveyor belt and to retain the material on the belt, preventing leakage. Such sealing systems are often used at transfer points between the end of one conveyor and the start of a second conveyor. Transfer points are found in such places as where the direction in which the material is being conveyed must be changed, where material from a main feed conveyor is emptied into a series of chutes and gates which may redirect the material onto one or more of a number of different conveyors, or where the conveyed material is taken through a processing step such as through a coal crusher.
As the conveyed material is loaded upon a conveyor belt, the material will sometimes overflow the edges of the belt causing large piles of the conveyed material to accumulate around the conveyor mechanism. Leakage from a conveyor belt requires expensive maintenance and clean up work in removing this fugitive material. Transfer points having permanently positioned conveyor belt skirts along the edges of a conveyor belt have been utilized to retain the conveyed material on the belt and to prevent transfer point leakage. Examples of such arrangements are illustrated in U.S. Pat. Nos. 4,236,628 and 4,874,082.
Such conveyor belt skirts are in contact with the conveyed material as the material is loaded onto the belt and as the material is conveyed along the belt. Due to the often abrasive qualities of the conveyed material, the inner surfaces of the conveyor belt skirts are exposed to extreme amounts of wear. Conveyor belt skirts are therefore normally lined with a wear resistant liner such as T-1 steel or ultra-high molecular weight plastic. These wear liners are usually attached to the interior of the skirts with countersunk bolts or by tack welding. When a wear resistant liner requires replacement, the conveyor must be shut down and the worn wear plates are individually removed from the conveyor belt skirts by a person working on the inside of a chute or within the transfer point. New wear plates are then bolted or welded in place from the inside of the transfer point. A person must work from the interior of the chute or transfer point in a small, dark and inconvenient area while replacing the wear plates. This often leads to long conveyor belt down times and to poor workmanship. The accuracy with which the wear resistant materials are replaced is impeded which leads to leakage of the conveyed material from the transfer point.
The stream of conveyed material which is being loaded onto a conveyor from another conveyor belt or from a chute is often not centered on the center line of the receiving conveyor belt. This causes the conveyed material to pile up on one side or the other of the receiving belt resulting in uneven belt loading conditions which causes unnecessary wear to the conveyor mechanism. Conveyor belt skirts can help redirect the stream of conveyed material back to the center line of the receiving conveyor. However, the repositioning of the stream of conveyed material causes extreme wear on the wear plates, requiring more frequent replacement of wear plates and further conveyor belt down time and wear plate misalignment.
As the conveyed material is transferred onto a conveyor, the material often falls from a substantial height above the conveyor belt. The conveyed material will impact the conveyor belt with a large force creating considerable amounts of dust. A dust collection system is often provided above the conveyor belt at points ahead of and after the zone where the conveyed material is loaded. The conveyor belt skirts help to seal this dust within the transfer point so that the dust can be collected by the dust collectors.
The problem of dust production is most acute at the conveyor belt surface as most of the dust is generated at the interface between the conveyor belt surface and the conveyed material. The dust which is created at the conveyor belt surface often becomes trapped from escaping upwardly by the continual downward flow of the conveyed material from above and from a seal which is created between the wear liner of the conveyor belt skirt and the conveyed material above the belt which is in contact with the skirt. This creates an area of positive pressure at the belt edge which tries to force the dust out of the transfer point between the edge of the conveyor belt and the conveyor belt skirt. The gap between the lower edge of the transfer point skirt and the edge of the conveyor belt is often a quarter of an inch. Maintaining a close tolerance on this gap is important to retaining the conveyed material and the dust which is produced from the loading.